The present invention relates generally to inkjet printheads, and more particularly to communicating signals to an inkjet printhead assembly with low voltage differential signaling.
A conventional inkjet printing system includes a printhead, an ink supply which supplies liquid ink to the printhead, and an electronic controller which controls the printhead. The printhead ejects ink drops through a plurality of orifices or nozzles and toward a print medium, such as a sheet of paper, so as to print onto the print medium. Typically, the orifices are arranged in one or more arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other.
Typically, the printhead ejects the ink drops through the nozzles by rapidly heating a small volume of ink located in vaporization chambers with small electric heaters, such as thin film resisters. Heating the ink causes the ink to vaporize and be ejected from the nozzles. Typically, for one dot of ink, a remote printhead controller typically located as part of the processing electronics of a printer, controls activation of an electrical current from a power supply external to the printhead. The electrical current is passed through a selected thin film resister to heat the ink in a corresponding selected vaporization chamber.
Advanced printhead designs now permit an increased number of nozzles to be implemented on a single printhead. Moreover, in one arrangement, commonly referred to as a wide-array inkjet printing system, a plurality of individual printheads, also referred to as printhead dies, are mounted on a single carrier. In these arrangements, a number of nozzles and, therefore, an overall number of ink drops which can be ejected per second is increased. Since the overall number of drops which can be ejected per second is increased, printing speed can be increased with a wide-array inkjet printing system and/or printheads having an increased number of nozzles.
As the number of nozzles on a single carrier or a single printhead increases, the number of corresponding thin film resisters which need to be electrically coupled to the remote printhead controller correspondingly increases, which results in a correspondingly large number of conductive paths carrying nozzle data, fire signals, and other data signals to the printheads. Voltage switching in the large number of signals carried on the conductive paths generates undesirable electromagnetic interference (EMI). In addition, the ejection of ink from the nozzles (i.e., firing of the nozzles) requires a switching on and off of a large amount of electrical current in a short amount of time. The switching on and off of nozzle current of a large number of nozzles simultaneously generates undesirable EMI.
The EMI generated as a result of voltage switching in the signals carried on the conductive paths and nozzle firing causes conductive paths, such as cables, to conduct and/or radiate undesirable EMI. EMI is undesirable because EMI interferes with internal components of the printing system and can also interfere with other electric devices and appliances not associated with the printing system, such as computers, radios, and televisions. Moreover, systems, such as printing systems, typically need to comply to an electromagnetic compliance (EMC) standard which defines limits to levels of stray EMI noise signals. For example, EMC standards are set by government regulatory agencies, such as the Federal Communications Commission (FCC), which set electrical emission standards for electric devices.
For reasons stated above and for other reasons presented in greater detail in the Description of the Preferred Embodiment section of the present specification, an inkjet printing system is desired which minimizes the amount of undesirable EMI conducted and/or radiated by the conductive paths which communicate data signals from the electronic controller to the printhead(s).
One aspect of the present invention provides an inkjet printhead assembly adapted to couple to cabling. The cabling is coupled to an electronic controller in an inkjet printing system. The inkjet printhead assembly includes low voltage differential signaling (LVDS) receivers adapted to couple to the cabling. The LVDS receivers receive first signals having LVDS levels and convert the first signals to second signals having second signaling levels. The inkjet printhead assembly includes electronics adapted to receive the second signals.